We haven't really searched for metric lead screws and nuts. I tried doing a cursory search for metric sized lead screws and nut with your specification of 12mm from the previous question and found it quite challenging. If you can't find the correct anti-backlash nut, I would recommend getting a 1/2" lead screw and anti-backlash nut and change your coupling to a 1/2" for the lead screw side and the bearings to 1/2" ID bearings.
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Where can I purchase metric anti-backlash nuts as I live in Australia?